The non-equilibrium solidification processes of industrial aluminum alloys AMg2 and AMg6 of Al-Mg-Mn system are studied by the method of thermal analysis. On the thermograms of crystallizing melts exothermic peaks which indicate the formation of the phases are revealed. The method of electron microprobe analysis showed the elemental composition of the phases in the cast samples. The connection between the position of exothermic peaks in the thermograms and the nature of phases evolved from the melt was revealed.